People rarely go and read the actual article so the headline must be accurate on its own or you misinform the public. Reversing or strongly altering the statement made in the headline in the actual article doesn't mean it is no longer misinformation, the damage is already done as the masses read the headline and now thinks it actually happened that way. Yet this seems to be completely acceptable even in most reputable news-sources.
The problem is not the existence or propagation of misinformation, disinformation or lies or truth. The problem is the attempt to control any of it by decree. You cannot trust anyone with the power to be the sole arbiter of truth. Everyone is human and everyone is fallible no matter how educated or credentialed. Democracy is the best of all the imperfect forms of government because it allows a plurality of opinions and convictions to exist and for everyone to freely choose among them. Governance can swing from one set of ideas to another peacefully and with the legitimacy that a majority have decided that things should be done a certain way for a limited amount of time after which we all re-evaluate the decision and can make changes if needed.
I think it's less about being factually wrong, and more about leading people to factually wrong conclusions with truthful statements.
Even just saying "X sells stock Y before event Z" imples that X knew about event Z and that it would affect the stock price of Y. People will read headlines like this and walk away assuming there was insider trading, but that may not be the case. Nothing in that example headline has to be false in order for it to spread falsehoods.
A lot of this type of misleading rhetoric often boils down to simply exploiting that many humans mistake correlation for causation and our education system really hasn’t don’t enough to hammer in not confusing those two.
Sure, that's a common technique, but would you really call it misinformation? I would call it misleading. Otherwise most of the financial press is misinformation and the word becomes kind of meaningless.